linux-kernel - [patch 1/2] PCI: add pci_resource

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Date:	Mon, 29 Sep 2008 09:56:56 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Len Brown <lenb@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Frans Pop <elendil@...net.nl>,
	Rene Herman <rene.herman@...access.nl>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
	Adam Belay <abelay@....edu>, Avuton Olrich <avuton@...il.com>,
	Karl Bellve <karl.bellve@...ssmed.edu>,
	Willem Riede <wriede@...de.org>,
	Matthew Hall <mhall@...omputing.net>
Subject: [patch 1/2] PCI: add pci_resource_enabled()

Add pci_resource_enabled() to determine whether a PCI BAR is
enabled.  Sometimes firmware leaves PCI BARs unconfigured, and
this interface is a way for the OS to identify that situation.
    
This is based on section 3.5 of the PCI Firmware spec, which says:
    
  Since not all devices may be configured prior to the operating
  system handoff, the operating system needs to know whether a
  specific BAR register has been configured by firmware. The operating
  system makes the determination by checking the I/O Enable, and
  Memory Enable bits in the device's command register, and Expansion
  ROM BAR enable bits. If the enable bit is set, then the corresponding
  resource register has been configured.
    
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@...com>

diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
index 1a5fc83..c4c90f8 100644
--- a/drivers/pci/setup-res.c
+++ b/drivers/pci/setup-res.c
@@ -26,6 +26,32 @@
 #include "pci.h"
 
 
+int pci_resource_enabled(struct pci_dev *dev, int bar)
+{
+	u16 command = 0;
+	u32 addr = 0;
+
+	/*
+	 * Based on section 3.5, "Device State at Firmware/Operating System
+	 * Handoff," in the PCI Firmware spec.
+	 */
+	pci_read_config_word(dev, PCI_COMMAND, &command);
+
+	if (pci_resource_flags(dev, bar) & IORESOURCE_IO)
+		return command & PCI_COMMAND_IO;
+
+	if (command & PCI_COMMAND_MEMORY) {
+		if (bar == PCI_ROM_RESOURCE) {
+			pci_read_config_dword(dev, dev->rom_base_reg, &addr);
+			return addr & PCI_ROM_ADDRESS_ENABLE;
+		}
+
+		return 1;
+	}
+
+	return 0;
+}
+
 void pci_update_resource(struct pci_dev *dev, struct resource *res, int resno)
 {
 	struct pci_bus_region region;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c0e1400..28ec520 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -796,6 +796,8 @@ static inline int pci_proc_domain(struct pci_bus *bus)
 }
 #endif /* CONFIG_PCI_DOMAINS */
 
+extern int pci_resource_enabled(struct pci_dev *dev, int bar);
+
 #else /* CONFIG_PCI is not enabled */
 
 /*
@@ -976,6 +978,9 @@ static inline struct pci_dev *pci_get_bus_and_slot(unsigned int bus,
 						unsigned int devfn)
 { return NULL; }
 
+static inline int pci_resource_enabled(struct pci_dev *dev, int bar)
+{ return 0; }
+
 #endif /* CONFIG_PCI */
 
 /* Include architecture-dependent settings and functions */
--
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